Just about one month ago, Microsoft Launcher hit 1 million downloads and was also marked down as the number one trending app in the Google Play Store. In the latest milestone for Microsoft's Andriod initiatives, Microsoft Launcher has hit 10 million downloads (via MSPoweruser.)
These most recent numbers are not officially coming from Microsoft, but instead, are noted on the Google Play Store listing for the launcher app. It's also just the latest Microsoft app which has proven to be popular amongst Android users, following Edge reaching 1 million downloads, and even Skype which is at 1 billion downloads.
Considering that there are over 2 billion monthly active Android users worldwide, this is just one small drop in the bucket for Microsoft. With Windows 10 Mobile being in maintenance mode, Microsoft is instead obviously is placing big bets on Android for the time being (pending Surface Phone?) especially given the rebrand of Arrow Launcher to Microsoft Launcher. In fact, the company even has plans to bring Cortana to Microsoft Launcher, and also the third party Cheetah CM Launcher.
You can find the download link for Microsoft Launcher below. Microsoft markets the launcher as a way to "maximize your mobile productivity" and personalize your Android device to match your own style. You can even use the launcher to access your calendar, documents, and recent activities in your personalized feed.